1. Field of the Invention
The present invention relates generally to an axial flow fan having auxiliary blades for use in combination with a shroud.
2. Description of the Prior Art
An ordinary type fan which is devoid of an auxiliary blade has been used in combination with a shroud for increasing the quantity of discharge air or for supplying a whole quantity of air introduced to a body to be cooled.
Meanwhile, the inventors have discovered axial flow fans having auxiliary blades (Japanese Utility Model applications Sho Nos. 50-152509, 23737, 58988, 58989, 58990), which produce strong centrifugal air streams by means of auxiliary blades. In combining an axial flow fan, according to these applications, with a shroud, the arrangement of the fan and the shroud has been studied so as to improve the quantity of discharged air and the noise level.
More particularly, the inventors have made tests and analysis for the purpose of establishing an optimum relationship or arrangement of an axial flow fan having an auxiliary blade relative to a shroud.